Safety switch and door lock for dishwashing machines



F. w. ROBSON 3,141,467

SAFETY SWITCH AND DOOR LOCK FOR DISHWASHING MACHINES July 21, 1964 2 Sheets-Sheet.- 1

Filed June 20, 1962 INVENTOR FREDERICK W, ROBSON ATTORNEYS July 21, 1964 F. w. ROBSON 3,141,467

SAFETY SWITCH AND DOOR LOCK FOR DISHWASHING MACHINES Filed June 20, 1962 2 Sheets-Sheet 2 INVENTOR. FREDERICK w. ROBSON ATTORNEYS United States Patent 3,141,467 SAFETY SWITCH AND DOOR LOCK FOR DTSHWASHING MACHINES Frederick W. Robson, Rochester, N.Y., assignor to Toledo Scale Corporation, Toledo, Ohio, a corporation of Ohio Filed June 20, 1962, Ser. No. 203,952 4 Claims. (Cl. 134-58) This invention relates to dishwashing machines and more particularly to safety mechanism for preventing scalding of operators by hot water during operation of such machines.

In commercial type dishwashing machines such as are used in restaurants, etc., it is customary to finally rinse dishes with very hot water which serves not only to rinse the dishes but also to sterilize them. If during operation of the rinsing mechanisms the doors of the machines are accidentally opened, hot rinse water is sprayed out into the open and can easily scald the operators.

To guard against such accidents, some dishwashing machines utilize the safety device disclosed in U.S. Patent No. 2,786,478 issued on March 26, 1957, to B. E. Robinson and R. 0. Bradley. The prior safety device includes a limit switch and switch-operating means operated by the door of the machine and prevents operation of the machine when the door is open. The prior safety device is generally unsatisfactory because of the complicated nature of its switch-operating means.

To guard against such accidents, other dishwashing machines utilize the safety device disclosed in US. Patent No. 2,782,793 issued on February 26, 1957, to R. 0. Bradley and B. E. Robinson. This prior safety device includes interlocking means mounted on the frame and on the door of the dishwashing machine which engage automatically when the door is closed and a solenoid operated latch that prevents disengagement of the interlocking means while the machine is in operation, thereby preventing opening of the door while hot water is being sprayed in the machine. This prior safety device is generally unsatisfactory because of its complicated structure.

Accordingly, the objects of this invention are to improve safety mechanisms for preventing scalding of dishwashing machine operators and to simplify the construction of such mechanisms.

One embodiment of this invention enabling the realization of these objects is a safety mechanism which includes a limit switch which is operated directly by the door of a dishwashing machine for preventing operation of the machine when the door is open. This is in contrast to prior safety switches which are operated by relatively complicated switch-operating means such as is disclosed in the above US. Patent No. 2,786,478. The safety mechanism can also include a door lock cooperating directly with the door of the dishwashing machine for preventing opening of the door while hot water is being sprayed in the machine. The door lock has superior simplicity compared to prior door locks such as is disclosed in the above US. Patent No. 2,782,793.

In accordance with the above, one feature of this invention resides in the simplified construction of the safety mechanism resulting in low cost structure and fool-proof operation.

Another feature resides in the cooperation of the safety mechanism directly with the door in such a manner that water leakage through the frame of the machine is obviated.

The above and other objects and features of this invention will be appreciated more fully from the following Patented July 21, 1964 detailed description when read with reference to the accompanying drawings wherein:

FIG. 1 is a perspective view of a dishwashing machine embodying the invention;

FIG. 2 is an enlarged perspective view of the safety mechanism shown atop the machine illustrated in FIG. 1;

FIG. 3 is an enlarged, fragmentary vertical sectional view taken along the line 33 of FIG. 1; and

FIG. 4 is an electrical wiring diagram of a control circuit for the machine illustrated in FIG. 1.

Referring to the drawings, a dishwashing machine embodying the invention includes a frame 10 having a washing and rinsing space enclosed by a vertically movable three-sided door 11. The frame 10 encloses a tank containing washing solution which is sprayed onto dishes placed in the washing and rinsing space above the tank through slotted wash spray tubes such as are shown in the above US. Patent No. 2,786,478. The washing solution from the tank returns to a pump 12, driven by a motor 13 (FIG. 4), which forces the Washing solution through the spray tubes. Additional rinse spray tubes, as also disclosed in the above US. Patent No. 2,786,478, are provided above and below the washing and rinsing space to supply hot rinse liquid from a fresh water supply directly onto the dishes for rinsing and sterilizing the dishes. Control of the rinsing operation is accomplished by an electrically-operated solenoid valve 14. Automatic operation of the washing and rinsing devices is initiated by pushing a start button 15 (FIGS. 1 and 4).

Operation of the start button 15, as hereinafter described in connection with FIG. 4, starts an automatic washing and rinsing cycle. To prevent operation of the machine when the door 11 is open, a normally open limit switch 16 having a switch operator 17 is provided. The switch 16 is enclosed in a housing 18 atop a roof 19 sup ported by posts 20, only one of which is shown (FIG. 3). The switch operator 17 extends from an opening 21 in the housing 18' and is arranged to be caught, when the door is closed, between a horizontal rim or edge 22 around the top of the three sides of the door 11 and the roof 19. This moves the switch operator 17 downwardly from its normal position and closes the normally open safety switch 16 to permit the automatic cycle to start after the start button 15 is pushed. When the door 11 is closed, the door rim 22 engages the edges of the roof 19 to seal in steam and water. The door rim 22 is so flexible that it humps up slightly at the switch operator 17 to allow room for the switch operator between the door rim 22 and the edge of the roof 19 and engages the roof edge at either side of the switch operator and the rest of the three roof edges to seal in the steam and Water. Opening of the door 11 allows the normally open switch 16 to open and stop operation of the machine.

One of the features of the invention resides in the superior simplicity of the means for operating the switch 16. In the above US. Patent No. 2,786,478, a safety switch is shown which is operated by a switch operator extending through the frame of the dishwashing machine into the interior. This invites leakage around the switch operator and because of the complicated nature of the switch operator it is of high cost and apt to get out of adjustment. The horizontal door rim 22 functions both to seal in steam and water and to operate the switch operator 17 and is the epitome of simplicity.

To prevent opening of the door 11 while hot water is being sprayed in the machine, a door lock 23 having a lock finger 24 is provided. The door lock 23 also is enclosed in the housing 18, the lock finger 24 extending from an opening in the housing 18 when the lock is in its door-locking position shown in FIGS. 1 and 3. The unlocked position of the lock is shown in FIG. 2. The lock finger 24 is fixed to an end of a rod 25, which is slidably supported in a stationarily mounted block 26, having its other end connected by means of a pin 27 to a pair of parallel links 28 which are connected in turn to the core of a lock solenoid 29 (FIG. 4). Hence, the solenoid core and the rod 25 move together as one. A coil spring 30 surrounds the rod 25 between the block 26 and vertical faces 31 of the links 28 and urges the lock finger 24 to the right as viewed in FIG. 2. Energization of the coil of the lock solenoid 29 causes the lock finger 24 to be moved into door-locking position, i.e., to the left as viewed in FIG. 2, in opposition to the spring 39. In the door locking position of the lock finger 24 shown in FIGS. 1 and 3, the lock finger 24 prevents upward movement of the door 11 by being closely juxtaposed to the horizontal door rim 22 just above the door rim. In the unlocked position of the lock finger 24 shown in FIG. 2, the lock finger by being drawn into the housing 18 no longer prevents such door movement. As hereinafter described in connection with FIG. 4, closing of the door 11 to close the safety switch 16 and depression of the start button 15 automatically causes energization of the lock solenoid 29 and, hence, automatic locking of the door 11. The lock 23 automatically is unlocked at the completion of the automatic washing and rinsing c cle.

Another of the features of the invention resides in the superior simplicity of the door lock 23 resulting in low cost structure and fool-proof operation. Nothing could be simpler than the cooperation of the lock finger 24 with the door rim 22.

In operation, before an automatic cycle can be begun, the door 11 must be closed to close the safety switch 16. A main control switch 32 is closed to close contacts 33 and 34. The control switch 32 is used so that any time after the cycle is begun it can be interrupted, if an emergency occurs. The start button 15 is depressed momentarily and current flows through a lead 35, a branch lead 36, the safety switch 16, the start button 15 and closed contacts 37 operated by a wash cam 38 to the coil of a relay 39, and to the opposite side of the line. The wash cam 38 is one of a plurality of cams on a shaft 40 which is driven by a timer motor 41. Current also flows through a lead 42 and closed contacts 43 operated by a setting-up cam 44 to energize the coil of the lock solenoid 29, through the timer motor 41 which rotates the earns 38 and 44 and a rinse cam 45 clockwise, and through a pilot light 46 which stays lit throughout the cycle. The energized lock solenoid 29 moves the lock finger 24 into its door locking position shown in FIGS. 1 and 3 and holds it in such position in opposition to the return spring 30 from the beginning to the end of the cycle.

When the relay 39 was energized, it closed its contacts 47 and 48. Current is by-passed around the start button 15 by flowing through the contacts 48 and the contacts 37 to the coil of the relay 39 to maintain it energized after the start button 15 is released. Current also flows through the contacts 48, a lead 49 and contacts 43 to keep the lock solenoid 29, the timer motor 41 and the pilot light 46 energized. With the closing of contacts 47, the wash motor 13 was energized causing the pump 12 to spray wash water through the wash spray tubes.

When the machine has been running about forty seconds, a finger controlled by the setting-up cam 44, drops off the high part of the cam thus opening the contacts 43 and closing contacts 51 to prepare the controls for what is soon to follow. Current now, instead of flowing through contacts 48, lead 49 and contacts 43 to energize the lock solenoid 29, the timer motor 41 and the pilot light 46, flows through a lead 52 and contacts 51 to energize the lock solenoid 29, the timer motor 41 and the pilot light 46.

About two seconds after the finger 50 drops 01f the 4 high part of the setting-up cam 44, a finger 53, controlled by the wash cam 38, does the same, thereby opening contacts 37. The opening of the contacts 37 breaks the current flow to the relay 39 causing it to open its contacts 47 and 48. When contacts 47 open, current to the wash motor 13 is shut off and the wash cycle is complete.

For the next five seconds, both the wash and rinse mechanism are shut off, but the pilot light 46, the timer motor 41, and the lock solenoid 29 remain energized by current passing through the lead 52 and through the closed contacts 51. After the five seconds dwell (period in which wash water drains from the dishes), a finger 54, controlled by the rinse cam 45, rides on the high spot of such cam 45 to close the normally open contacts 55. Closing of the contacts 55 permits current to flow through the lead 52 and contacts 55 to the coil of the rinse solenoid valve 14 to open the valve 14. Opening of the valve 14 permits water to flow under pressure through a hot water line 56 and the rinse spray tubes onto the dishes. Rinsing continues until the finger 54 drops off the high spot of the rinse cam 45 to open the normally open contacts 55 and cut-01f current flow to the rinse solenoid valve 14. At this time, the timer motor 41, the lock solenoid 29 and the pilot light 46 are still energized by current flowing through the lead 52 and contacts 51.

Three seconds after the rinse cycle ends, contacts 37 and 43 are again closed by their respective fingers 53 and 50 riding on the high spots of their respective cams. When the finger 50 causes contacts 43 to close again, it also causes contacts 51 to open. Opening of contacts 51 breaks current flow to the timer motor 41, the lock solenoid 29 and the pilot light 46. When the pilot light 46 goes out, it is a signal that the cycle has been completed and that the door lock 23 is unlocked.

Various modifications and changes in the details of construction may be made without departing from the spirit and scope of the invention.

Having described the invention, I claim:

1. In a dishwashing machine having a washing space and a roof thereabove, in combination, door means for enclosing and selectively exposing the space, the door means including a flexible rim engageable with the roof to seal in steam and Water, a switch operator which is caught between the rim and the roof when the door means is closed, whereby the switch operator is operated by the rim, and a safety switch operated by the switch operator and adapted, whenever the door means is moved to its exposing position, to prevent operation of the machine, the flexible rim when the door means is closed humping up slightly at the switch operator to allow room for the switch operator between the rim and the roof without breaking said steam and water seal.

2. In a dishwashing machine having a washing space and a roof thereabove, in combination, door means for enclosing and selectively exposing the space, the door means including a rim having upper and lower surfaces, the lower rim surface being engageable with the roof to seal in steam and water, a switch operator which is caught between the lower rim surface and the roof when the door means is closed, whereby the switch operator is operated by the rim, electrical means including a safety switch operated by the switch operator for controlling the machine, and a door lock which is locked and unlocked by the electrical means at the beginning and end, respectively, of a dishwashing cycle, the door lock including a finger engageable with the upper rim surface to prevent opening of the door means while the machine is in operation.

3. In a dishwashing machine having a washing space and a roof thereabove, in combination, door means for enclosing and selectively exposing the space, electrical means for controlling the machine, and a door lock which is locked and unlocked by the electrical means at the beginning and end, respectively, of a dishwashing cycle, the door lock including a housing atop the roof, a solenoid within the housing, the solenoid having a core moveable in a rectilinear path, and a lock finger operatively connected to the core and movable as one therewith in a rectilinear path, the finger being movable between an unlocked position and a locked position wherein it extends out of the housing to be engageable with the door means to prevent opening of the door means While the machine is in operation.

4. In a dishwashing machine according to claim 3 wherein the door means includes a rim engageable with the roof to seal in steam and water, and the lock finger is engageable with the rim to prevent said opening of the door means While the machine is in operation.

References Cited in the file of this patent UNITED STATES PATENTS Rataiczak et a1. Oct. 15, 1940 Messler May 5, 194 2 Pappas Jan. 3, 1950 Stanitz et al Nov. 18, 1952 Bradley et a1 Feb. 26, 1957 Robinson et a1 Mar. 26, 1957 Fox et a1. Aug. 2, 1960 Lyman Feb. 13, 1962 Pay Apr. 10, 1962 

1. IN A DISHWASHING MACHINE HAVING A WASHING SPACE AND A ROOF THEREABOVE, IN COMBINATION, DOOR MEANS FOR ENCLOSING AND SELECTIVELY EXPOSING THE SPACE, THE DOOR MEANS INCLUDING A FLEXIBLE RIM ENGAGEABLE WITH THE ROOF TO SEAL IN STEAM AND WATER, A SWITCH OPERATOR WHICH IS CAUGHT BETWEEN THE RIM AND THE ROOF WHEN THE DOOR MEANS IS CLOSED, WHEREBY THE SWITCH OPERATOR IS OPERATED BY THE RIM, AND A SAFETY SWITCH OPERATED BY THE SWITCH OPERATOR AND ADAPTED, WHENEVER THE DOOR MEANS IS MOVED TO ITS EXPOSING POSITION, TO PREVENT OPERATION OF THE MACHINE, THE FLEXIBLE RIM WHEN THE DOOR MEANS IS CLOSED HUMPING UP SLIGHTLY AT THE SWITCH OPERATOR TO ALLOW ROOM FOR THE SWITCH OPERATOR BETWEEN THE RIM AND THE ROOF WITHOUT BREAKING SAID STEAM AND WATER SEAL. 